Applicability of histopathological osteomyelitis evaluation score (HOES) in chronic osteomyelitis of the foot - A feasibility study.

BACKGROUND: Diagnosis and classification of chronic osteomyelitis is not based on any objective criteria. None of the available methods for this is completely reliable. Tienmann et al. (2014) has described the so called histopathological osteomyelitis evaluation score (HOES) to overcome this limitation. But this has not been externally validated or tested in cases with foot osteomyelitis. METHODS: We prospectively reviewed the histopathological samples of 30 consecutive patients (30 feet) with foot osteomyelitis managed operatively. There were 19 males and 11 females with an average age of 41.6 (range, 27-63) years. The underlying pathology was spina bifida in 12, Charcot's arthropathy in eleven and post-traumatic in seven patients. The bones involved were calcaneum, talus and fifth metatarsal. Pathological diagnosis was made based on HOES by a single pathologist blinded to the clinical diagnosis and both were compared. Intra- and inter-observer reliability of HOES was assessed by analysing the scores of each patient assigned independently by four different pathologists (blinded to the clinical diagnoses and to each other) at two different occasions one week apart. RESULTS: All samples showed features of long-standing osteomyelitis. When attempting to classify to "acute on chronic", "chronic" and "quiescent" forms, the pathological diagnosis correlatead with the clinical diagnosis only in 16 cases (53.3 percent). Histological classification to Tienmann's types as per the scoring system yielded three distinct pathological entities that had common histological features with regard to bone, soft tissue and inflammatory infiltration. HOES exhibited excellent intra- and inter-observer reliability. CONCLUSIONS: HOES is well applicable in foot osteomyelitis both for diagnosis and classification by unambiguous and precise scoring system. This makes diagnostic labelling more accurate and repeatable. The clinical relevance of these histopathological types in guiding management and determining prognosis needs to be investigated further.